This invention relates to a bifunctional lubricant additive which provides surprising dispersancy properties when employed in a single grade lubricating oil composition.
A problem other than dispersancy facing the lubricant manufacturer is that of seal deterioration in the engine. All internal combustion engines use elastomer seals, such as Viton seals, in their assembly. Over time, these seals are susceptible to serious deterioration caused by the lubricating oil composition. A lubricating oil composition that degrades the elastomer seals in an engine is unacceptable to engine manufacturers and has limited value.
An important property of a lubricating oil additive and a blended lubricating oil composition containing such additives is the compatibility of the oil composition with the rubber or elastomer seals employed in the engine. Nitrogen-containing succinimide dispersants employed in crankcase lubricating oil compositions typically have the effect of seriously degrading the rubber seals in internal combustion engines. In particular, such dispersants are known to attack Viton AK-6 rubber seals. This deterioration exhibits itself by sharply degrading the flexibility of the seals and increasing these hardness. This is such a critical problem that Volkswagen Corporation requires that al crankcase lubricating oils must pass a Viton Seal Compatibility Test before the oil composition will be rated acceptable for engine crankcase service. The polymeric dispersants of the present invention exhibit improved Viton Seal Compatibility is the trademark for a series of fluoroelastomers based on copolymers of vinylidene fluoride and hexafluoropropylene, produced by DuPont de Nemours, E. I. & Company of Wilmington, Del.